A few episodes into the final season of "The Shield" - one of television's finest achievements and a game-changer in the cop genre - Detective Vic Mackey (Michael Chiklis) finds himself in yet another complicated jam. The strain is wearing on him, the desperation more transparent than in the past. He jumps to his feet.

"I've got a card to play," he says, and bolts out the door.

Unfortunately for Mackey - who's played more shady cards than a backroom poker player - he's running out of them. In fact, one of television's most complicated, ethically challenged anti-heroes is about to be played out himself. In this final season, something has to give.

"The Shield" has always been about police corruption, bad choices for good reasons, human frailty, justice versus vengeance and the end justifying the means. In the very first episode, Mackey shoots another cop in cold blood. The next five seasons were about the fallout from that and a series of other ethical failures, including the hijacking of "the Armenian money train" - stealing the profits from a deadly Armenian gang - which has been the dramatic catalyst from Season 2 until the bitter end of this final season.

And anyone who doubts that "The Shield" will go out bitterly - and bloodily - hasn't been paying attention.

Gambling on 'Shield'

To fully appreciate the legacy of "The Shield," you have to go back to its premiere on the FX channel in March 2002, a time when there were roughly eight scripted series on basic cable, none on which had any gravitas. HBO had "The Sopranos," but the consensus was that high-end quality cable fare could exist only on a premium channel - one without commercials - because even toned down, the language, sex and violence of such a drama would discourage advertisers.

But FX believed in the ultra-gritty "Shield" and took the gamble. Backed by enormous critical praise, "The Shield" premiered to more than 5 million viewers, which shattered the basic-cable ratings record. FX's decision to boldly jump into the scripted-series business altered basic cable - and television - forever. Now everybody's in the game.

But not everybody has something like "The Shield" in its arsenal. With its fearless writing and the ferocious intensity of Chiklis leading the way, "The Shield" reinvented the cop genre. An argument can be made that "The Wire" and "The Shield" have so far surpassed the creative achievements of the great network cop series - "Homicide" and "NYPD Blue" specifically - that it would almost be pointless to attempt such a series now.

What remains compelling about "The Shield" as it heads into its last hurrah are the gray areas and ethical gradations of the characters that have defined it. Creator Shawn Ryan found, in the Vic Mackey character, a likable monster. Much in the way that Tony Soprano's actions conflicted viewers, Mackey's poisonous mix of God-complex-meets-sanctimonious-criminality is hard to turn away from. Mackey is the ultimate anti-hero on television right now.

The final season

Even in this last season, when we should all know better - when the drumbeat for justice (or something) for Mackey grows louder and more incessant, he's still able to sell you his good side. The season begins with Strike Team outcast Shane (Walton Goggins) trying to make up for his own past indiscretions with Mackey and to stop the Armenians from killing Mackey's family as revenge for the money train rip-off.

Shane - easily the most emotionally damaged member of the Strike Team because of what it has taken to cover up all the lies - thinks he's found a way to strike a deal and avert the vengeance. But Mackey, whose unpredictable moral compass has held viewers in awe all these seasons, can't abide the collateral damage that the deal may entail. "Do you think I'd let three random kids get killed in Chicago just to save my own?"

That one simple sentence illustrates Mackey perfectly.

Here's a guy who killed a fellow cop to cover up his own ethical deviations - a pattern of wanting and taking and justifying that grew ever more dangerous (and less gray) through the years. And yet the same guy rids the streets of Los Angeles of gangbangers and heinous criminals, loves his family and is loyal to his closest fellow cops. What kept "The Shield" moving forward and avoiding monotony is that Ryan and the writers continued to muddy the lines of acceptable behavior that had already forced the viewers to play a game of situational ethics while they watched at home.

It was as if Ryan said, "OK, you're comfortable with Mackey doing this. How about this? Hey, the strains of having an autistic child are compelling him to get a little money on the side from bad guys. That's all right, isn't it? But how about if we make him go two steps further?"

Each season, the noose around Mackey's neck tightened and loosened. The writers deftly played on our emotions - our feelings that Mackey needed to get nailed, but our relief when he squirmed out of the grasp of justice, or our satisfaction as the sanctimonious higher-ups bent on nailing Mackey also went beyond the letter of the law. Was their pursuit of justice any different than his?

It was the kind of institutional failure mixed with human foibles that we all understand and sometimes condone. "The Shield" gave us a visceral and intellectual account of the human condition under duress. It wasn't so simple as "What would you do?" It was, "How slippery is the slope when you're on it? Good people can do bad things, but how much bad is acceptable? Can deviant behavior that saves lives or rights a wrong be rationalized?"

But now it all ends. And with that comes judgment time. Does Mackey get caught and do time? Does he die? Is his family harmed? Does he walk away just in time? Or does he win, the money and the badge proving that the end justifies the means?

One thing is clear: There will be no vague finale, no unfinished business. It's not the way of "The Shield." And when it goes out, spare a moment of appreciation for a series that changed the way cable television looked at content.